Summary: Behavioral/Systems/Cognitive
Direction Discrimination Thresholds of Vestibular and
Cerebellar Nuclei Neurons
Sheng Liu,1 Tatyana Yakusheva,1 Gregory C. DeAngelis,2 and Dora E. Angelaki1
1Department of Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, and 2Department of Brain and Cognitive Sciences,
University of Rochester, Rochester, New York 14603
To understand the roles of the vestibular system in perceptual detection and discrimination of self-motion, it is critical to account for
response variability in computing the sensitivity of vestibular neurons. Here we study responses of neurons with no eye movement
sensitivity in the vestibular (VN) and rostral fastigial nuclei (FN) using high-frequency (2 Hz) oscillatory translational motion stimuli.
The axis of translation (i.e., heading) varied slowly (1°/s) in the horizontal plane as the animal was translated back and forth. Signal
detection theory was used to compute the threshold sensitivity of VN/FN neurons for discriminating small variations in heading around
all possible directions of translation. Across the population, minimum heading discrimination thresholds averaged 16.6° 1° SE for FN
neurons and 15.3° 2.2° SE for VN neurons, severalfold larger than perceptual thresholds for heading discrimination. In line with
previousstudiesandtheoreticalpredictions,maximumdiscriminabilitywasobservedfordirectionswherefiringratechangedsteeplyas
a function of heading, which occurs at headings approximately perpendicular to the maximum response direction. Forward/backward
heading thresholds tended to be lower than lateral motion thresholds, and the ratio of lateral over forward heading thresholds averaged
2.2 6.1 (geometric mean SD) for FN neurons and 1.1 4.4 for VN neurons. Our findings suggest that substantial pooling and/or
selective decoding of vestibular signals from the vestibular and deep cerebellar nuclei may be important components of further process-
ing. Such a characterization of neural sensitivity is critical for understanding how early stages of vestibular processing limit behavioral
performance.